Process Technology: An Introduction - Haan A.B. 2015

8 Absorption and stripping
8.2 The aim of absorption

Generally the commercial purpose of absorption processes can be divided into gas purification or product recovery, depending on whether the absorbed or the unabsorbed portion of the feed gas has the greater value. Typical gas purification applications are listed in Tab. 8.1. The removal CO₂ from synthesis gas in ammonia production and the removal of acid gases (CO₂ H₂S) from natural gas are some of the most widespread applications which are being improved continuously by the development of new solvents, process configurations and design techniques. In both applications stripping is used for absorbent regeneration.

Examples of absorption processes for product recovery are listed in Tab. 8.2. The absorption of SO₃ and NO_x in water to make concentrated sulfuric respectively nitric acid are probably the most widely-used product recovery applications of absorption. Other frequently encountered examples are the recovery of various products from a gaseous product stream by inert absorbents such as water. In some cases the absorber is used as a reactor where the desired chemical compound is obtained by a liquid phase reaction of the absorbed gases. An illustration of such a process is the production of urea from CO₂ and ammonia.

Tab. 8.1: Typical applications of absorption for gas purification.

Tab. 8.2: Typical applications of absorption for product recovery.